U.S. patent application number 09/994072 was filed with the patent office on 2003-05-29 for curable silicone compositions, methods and articles made therefrom.
This patent application is currently assigned to General Electric Company. Invention is credited to Gifford, Steven Kenneth, Lewis, Larry Neil, Rubinsztajn, Slawomir.
Application Number | 20030100669 09/994072 |
Document ID | / |
Family ID | 25540257 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030100669 |
Kind Code |
A1 |
Lewis, Larry Neil ; et
al. |
May 29, 2003 |
Curable silicone compositions, methods and articles made
therefrom
Abstract
A silicone composition that includes at least one functionalized
polydiorganosiloxane, at least one cure catalyst, at least one
reactive diluant, and at least one thermally conductive filler is
provided in the present invention. Further embodiments of the
present invention include a method for substantially increasing the
thermal conductivity of a silicone composition and a thermal
interface material containing the aforementioned silicone
composition.
Inventors: |
Lewis, Larry Neil; (Scotia,
NY) ; Gifford, Steven Kenneth; (Buskirk, NY) ;
Rubinsztajn, Slawomir; (Niskayuna, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY
GLOBAL RESEARCH CENTER
PATENT DOCKET RM. 4A59
PO BOX 8, BLDG. K-1 ROSS
NISKAYUNA
NY
12309
US
|
Assignee: |
General Electric Company
|
Family ID: |
25540257 |
Appl. No.: |
09/994072 |
Filed: |
November 27, 2001 |
Current U.S.
Class: |
524/588 |
Current CPC
Class: |
C08K 3/013 20180101;
C09D 183/04 20130101 |
Class at
Publication: |
524/588 |
International
Class: |
C08L 083/00 |
Claims
What is claimed is:
1. A silicone composition comprising a curable adhesive formulation
which comprises (A) a functionalized polydiorganosiloxane having
the general formula: (R.sup.1).sub.3-pR.sup.2.sub.pSiO
[(R.sup.1).sub.2SiO].sub.m[R.s-
up.1R.sup.2SiO].sub.nSi(R.sup.1).sub.3-qR.sup.2.sub.q wherein
R.sup.2 is independently at each occurrence vinylcyclohexeneoxy,
silane, epoxy, glycidoxy, acryloxy, imide, urethane, vinyl, or
combinations thereof; R.sup.1 is independently at each occurrence a
C.sub.1-8 alkyl radical, phenyl radical, vinyl radical, or
combination thereof; "p" is 0 or 1; "q" is 0 or 1; "m"+"n" has a
value sufficient to provide a polydiorganosiloxane with an initial
viscosity in a range between about 100 centipoise and about 50,000
centipoise at 25.degree. C.; (B) at least one reactive diluant; (C)
at least one cure catalyst; and (D) at least one thermally
conductive filler; wherein the total silicone composition has a
viscosity in a range between about 10,000 centipoise and about
250,000 centipoise at 25.degree. C. before cure.
2. The silicone composition in accordance with claim 1, wherein the
R.sup.2 is an acryloxy group.
3. The silicone composition in accordance with claim 1, wherein R1
is a methyl group.
4. The silicone composition in accordance with claim 1, wherein the
thermally conductive filler comprises silver, gold, copper,
platinum, nickel, aluminum oxide, aluminum nitride, boron nitride,
diamond, magnesium oxide, zinc oxide, zirconium oxide, or
combinations thereof.
5. The silicone composition in accordance with claim 4, wherein the
thermally conductive filler comprises silver.
6. The silicone composition in accordance with claim 1, wherein at
least one filler is present in a range between about 60% by weight
and about 95% by weight of the total silicone composition.
7. The silicone composition in accordance with claim 1, wherein the
diluant comprises tert-butyl-styrene,
methacryloxypropyltrimethoxysilane, methylmethacrylate,
hexanedioldiacrylate, glycidoxypropyltrimethoxysilane- , vinyl
ether, or combinations thereof.
8. The silicone composition in accordance with claim 7, wherein the
diluant comprises methacryloxypropyltrimethoxysilane.
9. The silicone composition in accordance with claim 7, wherein the
diluant comprises vinyl ether.
10. The silicone composition in accordance with claim 1, wherein
the diluant is present in a range between about 1% by weight and
about 20% by weight of the total silicone composition.
11. The silicone composition in accordance with claim 1, wherein
the cured composition provides a thermal conductivity greater than
about 1.5 W/mK.
12. The silicone composition in accordance with claim 1, wherein
the cured composition provides adhesion to at least one
substrate.
13. The silicone composition in accordance with claim 12, wherein
the substrate comprises silicon.
14. The silicone composition in accordance with claim 1, wherein
the curing catalyst comprises peroxide, onium salt, platinum
catalyst, or combinations thereof.
15. The silicone composition in accordance with claim 14, wherein
the curing catalyst comprises bisaryliodonium salt.
16. The silicone composition in accordance with claim 1, wherein
the catalyst is present in a range between about 10 parts per
million and about 10% by weight of the total silicone
composition.
17. The silicone composition in accordance with claim 1, which
further comprises an adhesion promoter.
18 The silicone composition in accordance with claim 17, wherein
the adhesion promoter comprises trialkoxyorganosilanes.
19. The silicone composition in accordance with claim 18, wherein
the trialkoxyorganosilane is .gamma.-aminopropyltrimethoxysilane,
glycidoxypropyltrimethoxysilane,
bis(trimethoxysilylpropyl)fumarate, or combinations thereof.
20. The silicone composition in accordance with claim 19, wherein
the trialkoxyorganosilane is
bis(trimethoxysilylpropyl)fumarate.
21 The silicone composition in accordance with claim 17, wherein
the adhesion promoter is present in a range between about 0.01% by
weight and about 1% by weight of the total silicone
composition.
22. The silicone composition in accordance with claim 1, which is
cured.
23. A silicone composition comprising a curable adhesive
formulation which comprises (A) a polydiorganosiloxane having the
general formula: (R.sup.1).sub.3-pR.sup.2.sub.pSiO
[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup-
.2SiO].sub.nSi(R.sup.1).sub.3-qR.sup.2.sub.q wherein R.sup.2 is
acryloxy group, R.sup.1 is methyl group, "p" is 0 or 1, "q" is 0 or
1, "m"+"n" has a value sufficient to provide a polydiorganosiloxane
with an initial viscosity in a range between about 100 centipoise
and about 50,000 centipoise at 25.degree. C.; (B) at least one
thermally conductive filler comprising silver; (C) at least one
diluant comprising methacryloxypropyltrimethoxysilane; (D) at least
one curing catalyst comprising bisaryliodonium salt; and (E)
optionally, at least one adhesion promoter comprising a
bis(trimethoxysilylpropyl)fumarate; wherein the total silicone
composition has a viscosity in a range between about 10,000
centipoise and about 250,000 centipoise at 25.degree. C. before
cure.
24. A method for substantially increasing the thermal conductivity
of a silicone composition comprising: providing at least one
functionalized polydiorganosiloxane wherein the
polydiorganosiloxane has the general formula:
(R.sup.1).sub.3-pR.sup.2.sub.pSiO [(R.sup.1).sub.2SiO].sub.m[R.s-
up.1R.sup.2SiO].sub.nSi(R.sup.1).sub.3-qR.sup.2.sub.q wherein
R.sup.2 is independently at each occurrence vinylcyclohexeneoxy,
silane, epoxy, glycidoxy, acryloxy, imide, urethane, vinyl, or
combinations thereof; R.sup.1 is independently at each occurrence a
C.sub.1-8 alkyl radical, phenyl radical, vinyl radical, or
combination thereof; "p" is 0 or 1; "q" is 0 or 1; "m"+"n" has a
value sufficient to provide a polydiorganosiloxane with an initial
viscosity in a range between about 100 centipoise and about 50,000
centipoise at 25.degree. C.; combining into the
polydiorganosiloxane at least one thermally conductive filler in a
range between about 60% by weight and about 95% by weight of the
total silicone composition; combining into the polydiorganosiloxane
at least one diluant; and combining into the polydiorganosiloxane
at least one cure catalyst wherein the total silicone composition
has a viscosity in a range between about 10,000 centipoise and
about 250,000 centipoise at 25.degree. C. before cure.
25. The method in accordance with claim 24, wherein the R.sup.2 is
an acryloxy group.
26. The method in accordance with claim 24, wherein R.sup.1 is a
methyl group.
27. The method in accordance with claim 24, wherein the thermally
conductive filler comprises silver, gold, copper, platinum, nickel,
aluminum oxide, aluminum nitride, boron nitride, diamond, magnesium
oxide, zinc oxide, zirconium oxide, or combinations thereof.
28. The method in accordance with claim 27, wherein the thermally
conductive filler comprises silver.
29. The method in accordance with claim 24, wherein at least one
filler is present in a range between about 60% by weight and about
95% by weight of the total silicone composition.
30. The method in accordance with claim 24, wherein the diluant
comprises tert-butyl-styrene, methacryloxypropyltrimethoxysilane,
methylmethacrylate, hexanedioldiacrylate,
glycidoxypropyltrimethoxysilane- , vinyl ether, or combinations
thereof.
31. The method in accordance with claim 30, wherein the diluant
comprises methacryloxypropyltrimethoxysilane.
32. The method in accordance with claim 30, wherein the diluant
comprises vinyl ether.
33. The method in accordance with claim 24, wherein the diluant is
present in a range between about 1% by weight and about 20% by
weight of the total silicone composition.
34. The method in accordance with claim 24, wherein the cured
composition provides a thermal conductivity greater than about 1.5
W/mK.
35. The method in accordance with claim 24, wherein the cured
composition provides adhesion to at least one substrate.
36. The method in accordance with claim 30, wherein the substrate
comprises silicon.
37. The method in accordance with claim 24, wherein the curing
catalyst comprises peroxide, onium salt, platinum catalyst, or
combinations thereof.
38. The method in accordance with claim 37, wherein the curing
catalyst comprises bisaryliodonium salt.
39. The method in accordance with claim 24, wherein the catalyst is
present in a range between about 10 parts per million and about 10%
by weight of the total silicone composition.
40. The method in accordance with claim 24, further comprising the
step of combining into the polydiorganosiloxane at least one
adhesion promoter.
41. The method in accordance with claim 40, wherein the adhesion
promoter comprises trialkoxyorganosilanes.
42. The method in accordance with claim 41, wherein the
trialkoxyorganosilane is .gamma.-aminopropyltrimethoxysilane,
glycidoxypropyltrimethoxysilane,
bis(trimethoxysilylpropyl)fumarate, or combinations thereof.
43. The method in accordance with claim 42, wherein the
trialkoxyorganosilane is bis(trimethoxysilylpropyl)fumarate.
44. The silicone composition in accordance with claim 40, wherein
the adhesion promoter is present in a range between about 0.01% by
weight and about 1% by weight of the total silicone
composition.
45. A method for increasing the thermal conductivity of a silicone
composition comprising: providing at least one polydiorganosiloxane
having the general formula: (R.sup.1).sub.3-pR.sup.2.sub.pSiO
[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup.2SiO].sub.nSi(R.sup.1).sub.3-qR.s-
up.2.sub.q wherein R.sup.2 is acryloxy group, R.sup.1 is methyl
group, "p" is 0 or 1, "q" is 0 or 1, "m"+"n" has a value sufficient
to provide a polydiorganosiloxane with an initial viscosity in a
range between about 100 centipoise and about 50,000 centipoise at
25.degree. C.; combining into the polydiorganosiloxane at least one
thermally conductive filler in a range between about 60% by weight
and about 95% by weight of the total silicone composition wherein
the filler comprises silver; combining into the
polydiorganosiloxane at least one diluant wherein the diluant
comprises methacryloxypropyltrimethoxysilane; combining into the
polydiorganosiloxane at least one cure catalyst wherein the cure
catalyst comprises bisaryliodonium salt; and optionally combining
into the polydiorganosiloxane at least one adhesion promoter
comprising bis(trimethoxysilylpropyl)fumarate wherein the total
silicone composition provides a viscosity in a range between about
10,000 centipoise and about 250,000 centipoise at 25.degree. C.
before cure and the cured composition provides a thermal
conductivity greater than about 1.5 W/mK.
46. A thermal interface material comprising: (A) (A) at least one
polydiorganosiloxane having the general formula:
(R.sup.1).sub.3-pR.sup.2- .sub.pSiO
[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup.2SiO].sub.nSi(R.sup.1).s-
ub.3-qR.sup.2.sub.q wherein R.sup.2 is independently at each
occurrence vinylcyclohexeneoxy, silane, epoxy, glycidoxy, acryloxy,
imide, urethane, vinyl, or combinations thereof; R.sup.1 is
independently at each occurrence a C.sub.1-8 alkyl radical, phenyl
radical, vinyl radical, or combination thereof; p is 0 or 1; "q" is
0 or 1; "m"+"n" has a value sufficient to provide a
polydiorganosiloxane with an initial viscosity in a range between
about 100 centipoise and about 50,000 centipoise at 25.degree. C.;
(B) at least one reactive diluant; (C) at least one cure catalyst;
and (D) at least one thermally conductive filler; wherein the
thermal interface material provides adhesion to at least one
substrate.
47. The thermal interface material in accordance with claim 46,
wherein the R.sup.2 is an acryloxy group.
48. The thermal interface material in accordance with claim 46,
wherein R.sup.1 is a methyl group.
49. The thermal interface material in accordance with claim 46,
wherein the thermally conductive filler comprises silver, gold,
copper, platinum, nickel, aluminum oxide, aluminum nitride, boron
nitride, diamond, magnesium oxide, zinc oxide, zirconium oxide, or
combinations thereof.
50. The thermal interface material in accordance with claim 49,
wherein the thermally conductive filler comprises silver.
51. The thermal interface material in accordance with claim 46,
wherein at least one filler is present in a range between about 70%
by weight and about 95% by weight of the total silicone
composition.
52. The thermal interface material in accordance with claim 46,
wherein the diluant comprises tert-butyl-styrene,
methacryloxypropyltrimethoxysil- ane, methylmethacrylate,
hexanedioldiacrylate, glycidoxypropyltrimethoxysi- lane, vinyl
ether, or combinations thereof.
53. The thermal interface material in accordance with claim 52,
wherein the diluant comprises
methacryloxypropyltrimethoxysilane.
54. The method in accordance with claim 52, wherein the diluant
comprises vinyl ether.
55. The thermal interface material in accordance with claim 46,
wherein the diluant is present in a range between about 1% by
weight and about 20% by weight of the total silicone
composition.
56. The thermal interface material in accordance with claim 46,
wherein the cured composition provides a thermal conductivity
greater than about 1.5 W/mK.
57. The thermal interface material in accordance with claim 46,
wherein the substrate comprises silicon.
58. The thermal interface material in accordance with claim 46,
wherein the cure catalyst comprises peroxide, onium salt, platinum
catalyst, or combinations thereof.
59. The thermal interface material in accordance with claim 58,
wherein the cure catalyst comprises bisaryliodonium salt.
60. The thermal interface material in accordance with claim 46,
wherein the catalyst is present in a range between about 10 parts
per million and about 10% by weight of the total silicone
composition.
61. The thermal interface material in accordance with claim 46,
which further comprises at least one adhesion promoter.
62. The thermal interface material in accordance with claim 61,
wherein the adhesion promoter comprises trialkoxyorganosilanes.
63. The thermal interface material in accordance with claim 62,
wherein the trialkoxyorganosilane is
.gamma.-aminopropyltrimethoxysilane,
glycidoxypropyltrimethoxysilane,
bis(trimethoxysilylpropyl)fumarate, or combinations thereof.
64. The thermal interface material in accordance with claim 63,
wherein the trialkoxyorganosilane is
bis(trimethoxysilylpropyl)fumarate.
65. The thermal interface material in accordance with claim 61,
wherein the adhesion promoter is present in a range between about
0.01% by weight and about 1% by weight of the total silicone
composition.
66. A thermal interface material comprising: (A) at least one
polydiorganosiloxane having the general formula:
(R.sup.1).sub.3-pR.sup.2- .sub.pSiO
[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup.2SiO].sub.nSi(R.sup.1).s-
ub.3-qR.sup.2.sub.q wherein R.sup.2 is acryloxy group, R.sup.1 is
methyl group, "p" is 0 or 1, "q" is 0 or 1, "m"+"n" has a value
sufficient to provide a polydiorganosiloxane with an initial
viscosity in a range between about 100 centipoise and about 50,000
centipoise at 25.degree. C.; (B) at least one thermally conductive
filler comprising silver; (C) at least one diluant comprising
methacryloxypropyltrimethoxysilane; (D) at least one cure catalyst
wherein the cure catalyst comprises bisaryliodonium salt; and (E)
optionally, at least one adhesion promoter comprising
bis(trimethoxysilylpropyl)fumarate wherein the thermal interface
material following curing of the silicone composition provides a
thermal conductivity greater than about 1.5 W/mK.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention is related to silicone compositions.
More particularly, the present invention is related to low
viscosity, curable polydiorganosiloxane compositions.
[0002] Dispensable materials that can cure and give high thermal
conductivity are typically used in the electronics industry.
Currently, there are two classes of cured articles used as
thermally conductive sinks. Sakamoto et al., Japanese Patent No.
05117598, discuss highly filled matrices that are cured to make a
pad. The pad can be cut and physically placed in an electronic
device. Toya, Japanese Patent No. 02097559, discusses a filled
matrix that is dispensed and cured in place. The dispensable
approach requires that the material have a viscosity that is low
enough such that the material can be forced through an orifice for
rapid manufacture of many parts. However, the final cured product
must have a sufficiently high thermal conductivity.
[0003] There remains a need to find a material that has a
sufficiently low viscosity such that it can be rapidly placed on a
small device with high power requirements. The high power
requirement needs a way to remove more heat. This requirement
necessitates a thermally conductive material. Thus, dispensable,
curable, and high thermally conductive materials are constantly
being sought.
BRIEF SUMMARY OF THE INVENTION
[0004] The present invention provides a silicone composition
comprising a curable adhesive formulation which comprises
[0005] (A) a functionalized polydiorganosiloxane having the general
formula:
(R.sup.1).sub.3-pR.sup.2.sub.pSiO
[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup.-
2SiO].sub.nSi(R.sup.1).sub.3-qR.sup.2.sub.q
[0006] wherein R.sup.2 is independently at each occurrence
vinylcyclohexeneoxy, silane, epoxy, glycidoxy, acryloxy, imide,
urethane, vinyl, or combinations thereof; R1 is independently at
each occurrence a C.sub.1-8 alkyl radical, phenyl radical, vinyl
radical, or combination thereof; "p" is 0 or 1; "q" is 0 or 1;
"m"+"n" has a value sufficient to provide a polydiorganosiloxane
with an initial viscosity in a range between about 100 centipoise
and about 50,000 centipoise at 25.degree. C.;
[0007] (B) at least one reactive diluant;
[0008] (C) at least one cure catalyst; and
[0009] (D) at least one thermally conductive filler;
[0010] wherein the total silicone composition has a viscosity in a
range between about 10,000 centipoise and about 250,000 centipoise
at 25.degree. C. before cure.
[0011] The present invention further provides a method for
increasing the thermal conductivity of a silicone composition
comprising:
[0012] (A) providing at least one functionalized
polydiorganosiloxane having the general formula:
(R.sup.1).sub.3-pR.sup.2.sub.pSiO[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup.2-
SiO].sub.nSi(R.sup.1).sub.3-qR.sup.2.sub.q
[0013] wherein R.sup.2 is independently at each occurrence
vinylcyclohexeneoxy, silane, epoxy, glycidoxy, acryloxy, imide,
urethane, vinyl, or combinations thereof; R.sup.1 is independently
at each occurrence a C.sub.1-8 alkyl radical, phenyl radical, vinyl
radical, or combination thereof; "p" is 0 or 1; "q" is 0 or 1;
"m"+"n" has a value sufficient to provide a polydiorganosiloxane
with an initial viscosity in a range between about 100 centipoise
and about 50,000 centipoise at 25.degree. C.;
[0014] combining into the polydiorganosiloxane at least one
thermally conductive filler in a range between about 60% by weight
and about 95% by weight of the total silicone composition;
[0015] combining into the polydiorganosiloxane at least one
diluant; and
[0016] combining into the polydiorganosiloxane at least one cure
catalyst wherein the total silicone composition has a viscosity in
a range between about 10,000 centipoise and about 250,000
centipoise at 25.degree. C. before cure.
[0017] In yet a further embodiment of the present invention, there
is provided a thermal interface material comprising:
[0018] (A) at least one polydiorganosiloxane having the general
formula:
(R.sup.1).sub.3-pR.sup.2.sub.pSiO[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup.2-
SiO].sub.nSi(R.sup.1).sub.3-qR.sup.2.sub.q
[0019] wherein R.sup.2 is independently at each occurrence
vinylcyclohexeneoxy, silane, epoxy, glycidoxy, acryloxy, imide,
urethane, vinyl, or combinations thereof; R.sup.1 is independently
at each occurrence a C.sub.1-8 alkyl radical, phenyl radical, vinyl
radical, or combination thereof; "p" is 0 or 1; "q" is 0 or 1;
"m"+"n" has a value sufficient to provide a polydiorganosiloxane
with an initial viscosity in a range between about 100 centipoise
and about 50,000 centipoise at 25.degree. C.;
[0020] (B) at least one reactive diluant;
[0021] (C) at least one cure catalyst; and
[0022] (D) at least one thermally conductive filler;
[0023] wherein the thermal interface material provides adhesion to
at least one substrate.
DETAILED DESCRIPTION OF THE INVENTION
[0024] It has been found that the use of at least one
functionalized polydiorganosiloxane, at least one reactive diluant,
at least one cure catalyst, and at least one thermally conductive
filler provides a formulation with a low viscosity of the total
silicone composition before cure and whose cured parts have a high
thermal conductivity. "High thermal conductivity" as used herein
refers to a cured total silicone composition with a thermal
conductivity greater than about 1.5 Watts per meter per degree
Kelvin (W/mK). "Low viscosity of the total silicone composition
before cure" typically refers to a viscosity of the composition in
a range between about 10,000 centipoise and about 250,000
centipoise and preferably, in a range between about 20,000
centipoise and about 100,000 centipoise at 25.degree. C. before the
silicone composition is cured. "Cured" as used herein refers to a
total silicone composition with reactive groups wherein in a range
between about 50% and about 100% of the reactive groups have
reacted.
[0025] The functionalized polydiorganosiloxane has the general
formula (I),
(R.sup.1).sub.3-pR.sup.2.sub.pSiO[(R.sup.1).sub.2SiO].sub.m[R.sup.1R.sup.2-
SiO].sub.nSi(R.sup.1).sub.3-qR.sup.2.sub.q (I)
[0026] wherein R.sup.2 is independently at each occurrence
vinylcyclohexeneoxy, silane, epoxy, glycidoxy, acryloxy, imide,
urethane, vinyl, or combination thereof; R.sup.1 is independently
at each occurrence a C.sub.1-8 alkyl radical, phenyl radical, vinyl
radical, or combination thereof; "p" is 0 or 1; "q" is 0 or 1;
"m"+"n" has a value sufficient to provide a polydiorganosiloxane
with an initial viscosity in a range between about 100 centipoise
and about 50,000 centipoise at 25.degree. C. and a functional
content in a range between about 1% by weight and about 10% by
weight of the functionalized polydiorganosiloxane. Radicals
represented by R.sup.1 are preferably C.sub.1-4 alkyl radicals and
more preferably, methyl. Typically, the functionalized
polydiorganosiloxane is present in a range between about 0.5% by
weight and about 5% by weight of the total silicone composition,
and more typically in a range between about 1% by weight and about
2% by weight of the total silicone composition.
[0027] Additionally, a reactive organic diluant may be added to the
silicone composition to decrease the viscosity of the composition.
Examples of diluants include, but are not limited to, styrene
monomers such as tert-butyl styrene (t-Bustyrene), (meth)acrylate
monomers such as methylmethacrylate and hexanedioldiacrylate,
methacryloxy-containing monomers such as
methacryloxypropyltrimethoxysilane, epoxy-containing monomers such
as biscyclohexaneoxyethylenetetramethylsiloxane,
glycidoxy-containing monomers such as
glycidoxypropyltrimethoxysilane, hydride-stopped
polydimethylsiloxanes, and vinyl ethers. It is to be understood
that (meth)acrylate includes both acrylates and methacrylates.
Vinyl ethers include mono-, di-, and poly-vinyl ethers containing
carbon atoms in a range between about 2 and about 20. The preferred
reactive diluants are methacryloxypropyltrimethoxysilane and vinyl
ethers. The mixture of the diluant and the functionalized
polydiorganosiloxane lowers the viscosity, which allows for higher
loading of thermally conductive filler. The amount of thermally
conductive filler in the silicone composition is directly
proportional to the thermal conductivity. Thus, the higher the
amount of thermally conductive filler in the silicone composition,
the greater the thermal conductivity of the silicone
composition.
[0028] The thermally conductive fillers in the present invention
include all common thermally conductive solids. Thermally
conductive fillers in the present invention include, for example,
forms of silver, gold, copper, nickel, platinum group metals, and
combinations thereof. Silver is the preferred thermally conductive
filler. Examples of thermally conductive silver include, but are
not limited to, silver powders, silver flakes, colloidal silver,
and combinations thereof. Further examples of thermally conductive
fillers include, but are not limited to, aluminum oxide, aluminum
nitride, boron nitride, diamond, magnesium oxide, zinc oxide, and
zirconium oxide. The filler is present in a range between about 60%
by weight and about 95% by weight of the total silicone
composition, more typically the filler is present in a range
between about 75% by weight and about 85% by weight of the total
silicone composition.
[0029] Inhibitors such as esters of maleic acid (e.g.
diallylmaleate, dimethylmaleate), acetylenic alcohols (e.g., 3,5
dimethyl-1-hexyn-3-ol and 2 methyl-3-butyn-2-ol), amines, and
tetravinyltetramethylcyclotetrasi- loxane and mixtures thereof can
also be employed when used in an effective amount which is
typically in a range between about 0.01% by weight and about 1% by
weight of the total silicone composition.
[0030] Adhesion promoters can also be employed such as
trialkoxyorganosilanes (e.g. .gamma.-aminopropyltrimethoxysilane,
glycidoxypropyltrimethoxysilane,
bis(trimethoxysilylpropyl)fumarate) used in an effective amount
which is typically in a range between about 0.01% by weight and
about 1% by weight of the total silicone composition. The preferred
adhesion promoter is bis(trimethoxysilylpropyl)fumarate.
[0031] Cure catalysts may also be present in the total silicone
composition that accelerates curing of the total silicone
composition. Typically, the catalyst is present in a range between
about 10 parts per million (ppm) and about 10% by weight of the
total silicone composition. Examples of cure catalysts include, but
are not limited to, peroxide catalysts such as
t-butylperoxybenzoate, onium catalysts such as bisaryliodonium
salts (e.g. bis(dodecylphenyliodonium hexafluoroantimonate,
(octyloxyphenyl, phenyl)iodonium hexafluoroantimonate,
bisaryliodonium tetrakis(pentafluorophenyl)borate),
triarylsulphonium salts, and platinum catalysts. Preferably, the
catalyst is a bisaryliodonium salt. Curing typically occurs at a
temperature in a range between about 50.degree. C. and about
175.degree. C., more typically in a range between about 100.degree.
C. and about 150.degree. C., at a pressure in a range between about
1 atmosphere (atm) and about 5 tons pressure per square inch, more
typically in a range between about 1 atmosphere and about 100
pounds per square inch (psi). In addition, curing may typically
occur over a period in a range between about 5 minutes and about 1
hour, and more typically in a range between about 15 minutes and
about 45 minutes.
[0032] The composition of the present invention may by hand mixed
but also can be mixed by standard mixing equipment such as dough
mixers, chain can mixers, planetary mixers, and the like.
[0033] The blending of the present invention can be performed in
batch, continuous, or semi-continuous mode. With a batch mode
reaction, for instance, all of the reactant components are combined
and reacted until most of the reactants are consumed. In order to
proceed, the reaction has to be stopped and additional reactant
added. With continuous conditions, the reaction does not have to be
stopped in order to add more reactants.
[0034] Thermally conductive materials as described in the present
invention are dispensable and have utility in devices in
electronics such as computers or in any device that generates heat
and where the device requires the heat to be efficiently removed.
The thermally conductive material is typically used as a thermal
interface material that provides adhesion to at least one substrate
such as silicon, gallium arsenide (GaAs), copper, nickel, and the
like.
[0035] In order that those skilled in the art will be better able
to practice the invention, the following examples are given by way
of illustration and not by way of limitation.
EXAMPLE 1
[0036] A base siloxane was prepared by combining as follows: 20
grams (g) of GE Silicones vinyl-stopped polydimethylsiloxane with
an average degree of polymerization of about 20, 5 g of GE
Silicones blend of a 1000 centipoise (cps) vinyl-stopped
polydimethylsiloxane and MDViQ resin, 1.7 g of GE Silicones MHQ
crosslinker containing about 1 wt % hydrogen, 9.1 g of Gelest, Inc.
intermediate DMSH03 which is H-stopped polydimethylsiloxane with an
average degree of polymerization of 5.1 and 0.85 g of catalyst. The
catalyst was pre-made and was composed of 87 milligrams (mg) of GE
Silicones platinum catalyst, 4.3 g of GE Silicones adhesion
promoter, 1.3 g of dibutylmaleate, 2.16 g of triallyl isocyanurate,
and 2.16 g of glycidoxypropyltrimethoxysilane.
EXAMPLE 2
[0037] The base siloxane in example 1 (9 g) was combined with
silver (38.4 g, 80/20 w/w silver powder/flake mixture of 80 parts
Technic silver powder 17-253 and 20 parts Ames Goldsmith 1024
silver flake to give a final formulation of 81% by weight in
silver). The silver-siloxane had a viscosity of 50,400 cps at 0.5
rotations per minute (rpm) as measured by a Brookfield Model DV-II
Cone & Plate Viscometer using a #52 cone. The mixture was cured
at 150.degree. C. for 30 minutes and had a thermal conductivity of
5.17 W/mK (5.42 W/mK on repeat) as measured by a Holometrix TCA
instrument.
EXAMPLE 3
[0038] The formulation prepared in Example 2 was repeated except
that only silver flake was used (i.e. no powder was used). The
initial viscosity was 80,000 cps. The thermal conductivity was
measured for two samples. In one reading, a value of 16.5 W/mK was
obtained and in the second reading, a value of 7.15 W/mK was
obtained.
EXAMPLE 4
[0039] A base formulation was prepared composed of a 50/50 w/w
mixture of Gelest Inc. intermediate DMSE21 (a glycidoxy-on-chain
polydimethylsiloxane copolymer) and 1,4-divinyloxybutane. The 50/50
mixture above was then combined with 2% by weight of GE Silicones
UV photoinitiator UV9380c. To the above polymer/catalyst mixture
was added the silver powder/flake mixture of 80 parts Technic
silver powder 17-253 and 20 parts Ames Goldsmith 1024 silver flake
to give a final formulation 81% by weight in silver. The initial
viscosity was 74,000 cps and the thermal conductivity of the cured
formulation was 5.24 W/mK (a second sample was made and gave a
thermal conductivity reading of 7.5 W/mK).
EXAMPLE 5
[0040] A base formulation was prepared composed of 50/50 w/w
mixture of Gelest Inc. intermediate UMS 182 (80-120 cps
acryloxy-on-chain polydimethylsiloxane copolymer) and
methacryloxypropyltrimethoxysilane. The 50/50 polymer mixture above
was combined with 2% by weight of t-butylperoxybenzoate. An 80/20
silver powder/flake mixture of Example 4 was combined with the
polymer catalyst mixture to make a formulation that was 81% by
weight silver. The initial viscosity was 47,000 cps and the thermal
conductivity of the cured formulation was 2.69 W/mK.
EXAMPLE 6
[0041] The polymer and silver formulation was prepared as in
example 5 except that in place of the t-butylperoxybenzoate
catalyst, UV 9380c as in example 4 was used. The formulation was
made two times: once with a viscosity of 41,000 cps and once with a
viscosity of 43,000 cps. The formulations were cured at 150.degree.
C. for 30 minutes in a Carver press at 5000 pounds per square inch.
The thermal conductivity was greater than 6 W/mK (triplicate
measurements) for both formulations.
[0042] While embodiments have been shown and described, various
modifications and substitutions may be made thereto without
departing from the spirit and the scope of the invention.
Accordingly, it is to be understood that the present invention has
been described by way of illustration and not limitation.
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